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高中《物理》上册在谈到绳子上的横波的形成时,说“把绳的一端固定,用手拿着另一端上下振动”即可。实际上,按照这种方法进行演示,效果很差,不可能得到如教材上的图8—24所绘的正弦波形。我们曾改用下述方法实验,效果不错。如附图所示,a 是一块长约25厘米的薄钢片,b 是细丝线,把 b 绑在 a 的尖端。用手将 a 的上部捏住,使 a 的下端离地1米左右,并让线的另一端自由放置于地面。演示时,手用力,迫使 a 振动起来。使钢片的振动接近简谐振动。这种振动,引起了波在绳子上的传播,看起来绳子上的波形就近似是一条正弦曲线。实验成功的关键是振子的频率不能过高,振幅不
In the book “Physics” in high school, when talking about the formation of a transverse wave on a rope, it is said that “fixing one end of the rope and shaking the other end up and down with your hand.” In fact, according to this method, the demonstration is very poor, and it is impossible to obtain the sinusoidal waveform as shown in Figures 8-24 of the textbook. We have used the following method to experiment, and the effect is good. As shown in the figure, a is a thin steel plate about 25 cm long, b is a thin wire, and the b is tied to the tip of a. Grasp the upper part of a by hand so that the lower end of a is about 1 meter off the ground and let the other end of the wire rest freely on the ground. During the demonstration, the hand is forced to force a to vibrate. The vibration of the steel sheet is close to simple harmonic vibration. This vibration causes waves to propagate on the rope. It appears that the waveform on the rope is approximately a sine curve. The key to the success of the experiment is that the frequency of the vibrator cannot be too high and the amplitude is not